Thao is from the Vietnamese Thảo (respectful, dutiful, filial) — also referring to the medicinal plant. Thao Pham — Vietnamese-American journalist. Thao Đình — Vietnamese artist. Princess Thao — Vietnamese imperial heritage naming.
Thao does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Thao reduce to 8, The Visionary. This is a traditional interpretive system, not a factual claim about the name.